Morristown National Historical Park lies at the junction between the Highland and Piedmont physiographic provinces, which follow both the coastline and the orientation of the Appalachians.
The Highlands are an extension of the New England Uplands and designate the eastern most edge of the Appalachians. These hills (also known as the Watchung Mountains or Hills), comprised mainly of gneiss, contain deposits of iron, graphite, and mica. On the eastern side of the uplands there is also an extension of hills known as the Trowbridge Range which are contained in what is called the Reading Prong. The Piedmont is the down sloping east side of the Uplands, which meets softer coastal-plain sediments.
Northern New Jersey was the southernmost limit of glacial advance during the Pleistocene era. The glacial features left in this area consist of a terminal moraine that runs across the grain of the uplands from northwest to southeast. North of the moraine glacial valleys were filled partially with debris, lakes were formed, and the uplands were scraped bare. South of the moraine drainages were infused by large amounts of melt water, creating fertile outwash plains.